1. Field of the Invention
The present invention relates to a chuck apparatus, which is capable of gripping a workpiece under an opening/closing action of a gripping member. More specifically, the invention concerns a chuck apparatus incorporating a detector therein that can detect an opening/closing amount of the gripping member.
2. Description of the Related Art
Heretofore, a chuck apparatus has been known, for example, which is mounted on the end of a shaft or the like of a machine tool. By performing opening/closing operations of a pair of gripping members, upon supplying a pressure fluid or an electric signal thereto, workpieces made up of various parts or the like are gripped by the chuck apparatus.
In this type of chuck apparatus, for example as disclosed in Japanese Laid-Open Patent Publication No. 11-114869, gripping of the workpiece is performed by controlling an opening/closing amount of the gripping members, corresponding to the size of the workpiece to be gripped. For this purpose, it is known to provide a detector, which is capable of detecting the opening/closing amount of the gripping members. In such a detector, the pair of gripping members is disposed on the upper surface of a displaceable guide rail, and the detector comprises a plurality of coils arranged along the guide rail. Further, in a similar manner, a plurality of other coils is disposed as well on the upper surface of an opposite side, sandwiching the guide rail therebetween. Additionally, by displacement of the gripping members between two coils, which are arranged in confronting positions sandwiching the guide rail, the amount of opening/closing of the gripping members is detected based on an induced output signal that is output.
However, in the aforementioned conventional technique, since the detector is constructed from plural coils, which are arranged along the displacement direction of the gripping members, an increase in the number of parts and a greater manufacturing cost for the chuck apparatus is incurred, and the apparatus becomes large in scale due to the coils, which are provided in plurality.